Handler 消息处理机制 简单语法介绍(内部)

//消息处理机制 Handler +Message +Looper+UI线程(主线程)Handler mHandler = new Handler() {    public void handleMessage(Message msg) {        switch (msg.what) {            case 3:                //btnLogin.setText("连接超时...");                toast = Toast.makeText(getApplicationContext(), "连接超时!", Toast.LENGTH_SHORT);                toast.show();                break;            case 2:                //btnLogin.setText("连接超时..");                toast = Toast.makeText(getApplicationContext(), "连接超时!", Toast.LENGTH_SHORT);                toast.show();                break;            case 1:                //Toast.makeText(MainActivity.this, "toast", Toast.LENGTH_SHORT).show();                progressDialog.setMessage("数据获取异常");                progressDialog.show();                //btnLogin.setText("登录");                //btnLogin.setClickable(true);                if (toast != null) {                    toast.cancel();                    toast = Toast.makeText(getApplicationContext(), "数据获取异常!", Toast.LENGTH_SHORT);                } else {                    toast = Toast.makeText(getApplicationContext(), "数据获取异常!", Toast.LENGTH_SHORT);                }                toast.show();                break;            case 0:                //progressDialog.setMessage("登录成功..稍后!");                //progressDialog.show();                //btnLogin.setText("登录成功");                //btnLogin.setClickable(false);                break;        }        super.handleMessage(msg);    }};